Minnesota Special Engineer Boiler License Practice Exam

What should be done if the isolating valve for the expansion tank is closed?

1. Open the valve immediately

2. It causes the safety relief valve to open

3. Shut down the boiler

4. Visually inspect the boiler

The correct answer is: It causes the safety relief valve to open

The correct action when the isolating valve for the expansion tank is closed is to recognize the implications of that closure on the system's operation. When this valve is closed, it can create a situation where pressure builds up in the expansion tank. As the liquid in the system heats up, the increase in volume and pressure may exceed safe limits, forcing the safety relief valve to open to prevent potential damage or failure in the boiler system. Understanding the role of the expansion tank is critical to maintaining system integrity. The expansion tank is designed to accommodate the increase in water volume due to heating, and closing the isolating valve negates its function, leading to dangerous operational conditions. Therefore, recognizing that the valve closure can trigger the safety relief valve to operate highlights the need for careful monitoring of these components to ensure safe and efficient boiler operation. While other actions may be considered, they do not directly address the consequence of a closed isolating valve in relation to system pressure management and safety.